This invention relates to a method for preparing carboxy functional silicones. More particularly, this invention relates to a method for preparing carboxy functional silicones from silane derivatives of alpha-olefin terminated-organic acids.
Carboxy functional silicones are useful in many applications where water- and alcohol-soluble organopolysiloxanes are desirable. For example, they are useful as emulsifying agents for the formation of aqueous emulsions of conventional organopolysiloxane fluids and in applications such as alcohol base cosmetics. Carboxy functional silicones can also function as reactants in the preparation of polysiloxane-polyether copolymer surfactants which are useful as additiives in polyurethane foam.
Carboxy-functional silicones and methods for preparing them are known in the art. Reference is made, for example, to U.S. Pat. Nos. 3,182,076 and 3,629,165, both to Holdstock. In the Holdstock method, carboxy-functional silicones are prepared by the hydrolysis and condensation of a mixture containing organotrichlorosilane, a diorganodichlorosilane, and a cyanoalkyldiorganochlorosilane. During the hydrolysis and condensation of these reactants, the various silicon-bonded chlorine atoms are replaced by silicon-bonded hydroxyl groups which intercondense to form siloxane linkages. The nitrile radical hydrolyzes to a carboxyl radical. Hydrochloric acid is also formed in the hydrolysis reaction.
One drawback to the prior art method described above is that cyano silanes are quite expensive and require the use of acrylonitrile, which is undesirable. In addition, the highly acidic media, i.e., concentrated hydrochloric acid required to perform the hydrolysis in the Holdstock method, is extremely corrosive and causes equipment problems.
It would be desirable, therefore, to provide a method for preparing carboxy functional silicones which does not require the use of either cyano silanes or acidic catalysts.